I personally would wait until the new cards arrive, especially since they may cost around the same as a 8800GTX costs now (as you say)..
It's just a few months wait, and you'll get sooooo much for for the same amount of cash if you just have some patience..
I almost regret getting a 8800 GTS GS a few months ago now..
But the good thing is that the 8800 GTS will probably drop quite a bit in price when the new cards arrive, and I'll certainly consider getting a second 8800 GTS to run SLI if they do..
